renovate: group golangci-lint updates

Currently, the golangci-lint update does not contain the update in
the GH action files. The reason is a packageRule which
combines and schedules all GH action version updates.

This commit introduces the necessary grouping packageRule which
combines all golangci-lint updates over all files.

Being further down in the list of package rules, this one gets selected.

Signed-off-by: Marco Hofstetter <marco.hofstetter@isovalent.com>

.github/renovate.json5

@@ -217,6 +217,14 @@
         "quay.io/cilium/hubble"
       ],
     },
+    {
+      // Group golangci-lint updates to overrule grouping of version updates in the GHA files.
+      // Without this, golangci-lint updates are not in sync for GHA files and other usages.
+      "groupName": "golangci-lint",
+      "matchDepNames": [
+        "golangci/golangci-lint"
+      ]
+    },
     {
       // Do not allow any updates into stable branches.
       "enabled": false,